I think pari might be from par, paris, the adjective (like/equal), rather than from pario. If so, then pari is singular ablative and can agree with calamitate. Then pari calamitate could mean by an equal misfortune, which is ablative of means. Thus, they are asking Jove to effect or weaken eos (whoever they are) by means of a similar disaster.

The "eos" refers back to the people who can't live alone. This is the story of Deucalion and Pyrrha. Jove has killed off all the other people except them so there are no other people in existence at this point in the story.

They are asking Jove to do one of two things. Either bring people back or this "pari calamitate" option. From what you guys have said, it sounds like the best way to understand this second option is that if D & P can't have other people to live with, they'd like Jove to destroy them the way he did all the other people.

As we have discussed in some recent threads, the reflexive pronouns can be quite vague. Here, if we were to use se instead of eos, it would probably be referring back to "Jove", and that is not the intended effect.

I agree with Yvonne on this. A&G has an interesting section on this as well that might clarify some of this ambiguity.